This invention relates to twin proportioning valves including two correcting valves notably adapted to be separately connected to two independent hydraulic braking sub-circuits of a vehicle each hydraulic valve being of the type comprising a movable differential piston. Such twin valves may be used particularly in diagonal brake circuits to control the rear axle braking forces.
There are known twin valves comprising two hydraulic proportioning valves, wherein the differential pistons are mounted in separate housings and are operatively connected to resilient return means by a mechanical linkage. This separate housing structure presents two main drawbacks : in effect manufacturing is rather expensive and the adjustment of the mechanical linkage in order to obtain substantially equal knee-point pressures is rather difficult and furthermore can only occur after mounting of the two valve housings on the vehicle. This last problem is critical when the twin valve is used in a diagonal circuit due to the fact the kneepoint pressures and the characteristic slopes of the proportioning valves should be the same.